Phase lock loop (PLL) synchronization

ABSTRACT

In an embodiment, an apparatus includes a first integrated circuit (IC) chip configured to receive a timing signal and a reference clock signal; a second IC chip configured to receive the timing signal from the first IC chip and the reference clock signal; and a third IC chip configured to receive the timing signal from the second IC chip and the reference clock signal. The second IC chip is electrically coupled between the first and third IC chips. The first, second, and third IC chips include respectively first, second, and third phase lock loop (PLL). The first, second, and third IC chips are configured to generate respective first, second, and third reference time signals based on the timing signal and the reference clock signal. The first, second, and third PLLs are synchronized to each other based on the respective first, second, and third reference time signals.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 62/982,998 filed Feb. 28, 2020 entitled “Phase Lock Loop(PLL) Synchronization” and U.S. Provisional Patent Application No.62/847,833 filed May 14, 2019 entitled “Chip to Chip TimeSynchronization,” the contents of which are hereby incorporated byreference in their entirety.

BACKGROUND

An antenna (such as a dipole antenna) typically generates radiation in apattern that has a preferred direction. For example, the generatedradiation pattern is stronger in some directions and weaker in otherdirections. Likewise, when receiving electromagnetic signals, theantenna has the same preferred direction. Signal quality (e.g., signalto noise ratio or SNR), whether in transmitting or receiving scenarios,can be improved by aligning the preferred direction of the antenna witha direction of the target or source of the signal. However, it is oftenimpractical to physically reorient the antenna with respect to thetarget or source of the signal. Additionally, the exact location of thesource/target may not be known. To overcome some of the aboveshortcomings of the antenna, a phased array antenna can be formed from aset of antenna elements to simulate a large directional antenna. Anadvantage of a phased array antenna is its ability to transmit and/orreceive signals in a preferred direction (e.g., the antenna'sbeamforming ability) without physical repositioning or reorientating.

It would be advantageous to configure phased array antennas havingincreased bandwidth while maintaining a high ratio of the main lobepower to the side lobe power. Likewise, it would be advantageous toconfigure phased array antennas and/or associated circuitry to operatetogether as to reduce signal degradation or introduction of signalerrors. It would be further advantageous to configure phased arrayantennas and/or associated circuitry having reduced weight, reducedsize, lower manufacturing cost, and/or lower power requirements.Accordingly, embodiments of the present disclosure are directed to theseand other improvements in phased array antenna systems or portionsthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thepresent disclosure will become more readily appreciated as the samebecome better understood by reference to the following detaileddescription, when taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is an example illustration of a block diagram showing a daisychain of integrated circuit (IC) chips configured to facilitate timingsignal distribution in accordance with some embodiments of the presentdisclosure.

FIG. 2A is an example illustration of a block diagram showing generationof a first level reference time in each chip of the plurality of ICchips in accordance with some embodiments of the present disclosure.

FIG. 2B is an example illustration of a waveform diagram associated withgeneration of the first level reference time in each chip in accordancewith some embodiments of the present disclosure.

FIG. 3 is an example illustration of a block diagram showing generationof a second level reference time in a chip in accordance with someembodiments of the present disclosure.

FIG. 4A is an example illustration of a block diagram showing generationof a modified second level reference time in a chip in accordance withsome embodiments of the present disclosure.

FIG. 4B illustrates example clock signals in accordance with someembodiments of the present disclosure.

FIG. 4C illustrates a block diagram showing an example use of the firstlevel reference time signal, second level reference time signal, ormodified second level reference time signal in accordance with someembodiments of the present disclosure.

FIG. 5 is an example illustration of an IC chip included in theplurality of IC chips in accordance with some embodiments of the presentdisclosure.

FIG. 6 is an example illustration of a top view of an antenna lattice inaccordance with some embodiments of the present disclosure.

FIG. 7 is an example illustration of a block diagram showing a circuitryor component section associated with a RF PLL synchronization scheme inaccordance with some embodiments of the present disclosure.

FIG. 8 is an example illustration of a block diagram showing circuitryor components included in the RF PLL of FIG. 7 in accordance with someembodiments of the present disclosure.

FIG. 9 is an example illustration of a block diagram showing additionalcircuitry or component details of the RF PLL of FIG. 8 in accordancewith some embodiments of the present disclosure.

FIG. 10 is an example illustration of divider ratios over time in aplurality of IC chips in accordance with some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

Embodiments of apparatuses and methods disclosed herein relate to phaselock loop (PLL) synchronization. In an embodiment, an apparatus includesa first integrated circuit (IC) chip configured to receive a timingsignal and a reference clock signal; a second IC chip configured toreceive the timing signal from the first IC chip and the reference clocksignal; and a third IC chip configured to receive the timing signal fromthe second IC chip and the reference clock signal. The second IC chip iselectrically coupled between the first and third IC chips. The first,second, and third IC chips include respectively first, second, and thirdphase lock loop (PLL). The first, second, and third IC chips areconfigured to generate respective first, second, and third referencetime signals based on the timing signal and the reference clock signal.The first, second, and third PLLs are synchronized to each other basedon the respective first, second, and third reference time signals. Theseand other aspects of the present disclosure will be more fully describedbelow.

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and will be describedherein in detail. It should be understood, however, that there is nointent to limit the concepts of the present disclosure to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives consistent with the presentdisclosure and the appended claims.

References in the specification to “one embodiment,” “an embodiment,”“an illustrative embodiment,” etc., indicate that the embodimentdescribed may include a particular feature, structure, orcharacteristic, but every embodiment may or may not necessarily includethat particular feature, structure, or characteristic. Moreover, suchphrases are not necessarily referring to the same embodiment. Further,when a particular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to affect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described. Additionally, it should be appreciated that itemsincluded in a list in the form of “at least one A, B, and C” can mean(A); (B); (C); (A and B); (B and C); (A and C); or (A, B, and C).Similarly, items listed in the form of “at least one of A, B, or C” canmean (A); (B); (C); (A and B); (B and C); (A and C); or (A, B, and C).

Language such as “top surface”, “bottom surface”, “vertical”,“horizontal”, and “lateral” in the present disclosure is meant toprovide orientation for the reader with reference to the drawings and isnot intended to be the required orientation of the components or toimpart orientation limitations into the claims.

In the drawings, some structural or method features may be shown inspecific arrangements and/or orderings. However, it should beappreciated that such specific arrangements and/or orderings may not berequired. Rather, in some embodiments, such features may be arranged ina different manner and/or order than shown in the illustrative figures.Additionally, the inclusion of a structural or method feature in aparticular figure is not meant to imply that such feature is required inall embodiments and, in some embodiments, it may not be included or maybe combined with other features.

Many embodiments of the technology described herein may take the form ofcomputer- or processor-executable instructions, including routinesexecuted by a programmable computer, processor, controller, chip, and/orthe like. Those skilled in the relevant art will appreciate that thetechnology can be practiced on computer/controller systems other thanthose shown and described above. The technology can be embodied in aspecial-purpose computer, controller, or processor that is specificallyprogrammed, configured or constructed to perform one or more of thecomputer-executable instructions described above. Accordingly, the terms“computer,” “controller,” “processor,” or the like as generally usedherein refer to any data processor and can include Internet appliancesand hand-held devices (including palm-top computers, wearable computers,cellular or mobile phones, multi-processor systems, processor-based orprogrammable consumer electronics, network computers, mini computers,and the like). Information handled by these computers can be presentedat any suitable display medium, including an organic light emittingdiode (OLED) display or liquid crystal display (LCD).

FIG. 1 is an example illustration of a block diagram showing a daisychain of integrated circuit (IC) chips configured to facilitate timingsignal distribution in accordance with some embodiments of the presentdisclosure. Each chip of the plurality of IC chips 100 is identical orsimilar to each other. Each chip of a plurality of IC chips 100 isserially or sequentially electrically coupled with each other, therebyforming a daisy chain of chips. The plurality of IC chips 100 comprisesP number of chips. A chip 102 (denoted as chip 1 or the first chip), achip 104 (denoted as chip 2 or the second chip), and a chip 106 (denotedas chip P or the last chip) of the plurality of IC chips 100 are shownin FIG. 1.

A modem 108 is configured to provide a timing signal, also referred toas L1sync, to chip 102. The timing signal comprises a low frequencysynchronization signal that has a square wave or a step wave shape. Areference clock 110 is configured to provide a reference clock signal toeach chip of the plurality of IP chips 100. The reference clock signalcomprises a differential sinusoidal wave signal or a single-endedsinusoidal signal. In response, circuitry 103 included in chip 102 isconfigured to distribute or share the timing signal with the next chipin the daisy chain, namely, chip 104. Circuitry 103 includes one or moreamplifiers, amplifiers/buffers, flip-flops, and/or other electricalcomponents arranged as shown in FIG. 1. In some embodiments, a signalpathway length between adjacent chips may be in the order ofapproximately 10 centimeter (cm).

Circuitry 105 included in chip 104, in turn, distributes the timingsignal (L1sync) received from chip 102 to the next chip in the daisychain (e.g., to chip 3). The nth chip distributes the timing signalL1sync to the n+1th chip, including to the last chip 106 includingcircuitry 107 similar to circuitry 103, 105.

Hence, the same timing signal L1sync is distributed to each chip of theplurality of IC chips 100. The timing signal L1sync is respectivelydistributed among the chips 100 with a predictable or known link—apredictable chip-to-chip distance. When modem 108 generates the nexttiming signal, such timing signal is similarly distributed from chip 1,chip 2, and so forth, to chip P as described above.

In some embodiments, each chip of the plurality of IC chips 100 alsoincludes circuitry or components configured to use the timing signalL1sync. For instance, without limitation, circuitry/component sections113, 115, and 117 included in respective chips 102, 104, and 106 may usethe timing signal L1sync.

FIG. 2A is an example illustration of a block diagram showing generationof a first level reference time in each chip of the plurality of ICchips 100 in accordance with some embodiments of the present disclosure.FIG. 2B is an example illustration of a waveform diagram associated withgeneration of the first level reference time in each chip in accordancewith some embodiments of the present disclosure. Referring to FIG. 2A,chips 240 and 242 comprise chips of the plurality of IC chips 100arranged in a daisy chain arrangement. Chip 240 may comprise the nthchip (where n<P) and chip 242 may comprise the Pth or last chip in thedaisy chain arrangement. In some embodiments, chips 240, 242 may besimilar to respective chips 104, 106.

Each chip of the plurality of IC chips 100 includes one or morecircuitry or component sections. For example, without limitation, chip240 includes a circuitry section similar to circuitry 105 (not shown inFIG. 2A) and a circuitry/component section 208. If chip 240 compriseschip 104 of FIG. 1, then section 208 comprises section 115. Chip 240receives the timing signal (L1sync) from the immediately preceding chip(the n−1th chip), the reference clock signal (sinus_refclk) from thereference clock 110, and a reset signal from modem 108. Chip 240 isconfigured to distribute the timing signal (L1sync) to the next chip(the n+1th chip) as described above in connection with FIG. 1. Chip 240is further configured to generate a first level reference time signal(L1_reference_time). Each chip of the plurality of IC chips 100 mayinclude circuitry and/or components such as circuitry 105 and section208.

In some embodiments, section 208 included in chip 240 is configured toreceive the timing signal (L1sync) from the immediately preceding chipat a subsection 200, perform appropriate signal processing (e.g., signalamplification, buffering, etc.) within subsection 200, and provide thetiming signal to a counter 202. The reference clock signal(sinus_refclk) is received by an amplifier/buffer 204 included insection 208. In some embodiments, amplifier/buffer 204 is configured toconvert the reference clock signal, which has a sinusoidal waveformshape, into a converted reference clock signal (refclk) having a squarewaveform. The amplifier/buffer 204 may be part of a Schmitt triggercircuit, for example, to perform the waveform shape conversion. Theconverted reference clock signal is also an input to counter 202. Thereset signal (rstn) is an input to subsection 206 included in section208, which processes the reset signal as necessary, and then providesthe (processed) reset signal as an input to counter 202.

Although not shown, section 208 can further include associatedelectrical components and/or elements such as, but not limited to,buffers, digital flops, passive electrical elements, resistors,inductors, capacitors, feedback loops, and/or the like to process one ormore of the input signals (e.g., timing signal, reference clock signal,reset signal) into formats suitable to be inputs to the counter 202.

As shown in FIG. 2B, the reference clock signal (sinus_refclk) isrepresented as a waveform 210 having a sinusoidal wave shape. As anexample, the reference clock signal can have a frequency in the range ofa few Megahertz (MHz) to a few hundred MHz. The reference clock signalcomprises a continuous signal having a constant periodicity. Waveform212, having a square wave shape, represents the converted referenceclock signal (refclk). The converted reference clock signal retains thesame period as the reference clock signal (e.g., both waveforms 210 and212 have the same period 222). Waveform 214 having a step (or square)wave shape comprises the reset signal. Waveform 216 having a step (orsquare) wave shape comprises the timing signal (L1sync). As an example,the period associated with the timing signal may be a few kilohertz(kHz).

Counter 202, also referred to as a L1_time_counter, is configured togenerate and output the first level (L1) reference time signal based onthe timing signal, converted reference clock signal, and reset signal.The first level reference time signal is also referred to asL1_reference_time, a L1_reference_timing signal, or the like. Counter202 is configured to count the number of cycles, periods, or pulses ofthe converted reference clock signal received starting from a particularpoint in time as specified by the timing signal (L1sync). The timingsignal (L1sync) changing to a high (or is at a rising edge) can comprisethe particular point in time at which counter 202 is triggered to startcounting the converted reference clock signal. This count is specifiedin the first level reference time signal. Because counter 202continuously counts the number of cycles/periods/pulses of the convertedreference clock signal, the first level reference time signalcorrespondingly provides the present or real-time count value.

In some embodiments, counter 202 counts during the timing signal'speriod and automatically resets to zero to start counting again startingat the point in time at which the next rising edge (or high) of thetiming signal occurs. Thus, the count performed by counter 202 followsor tracks the periodicity of the timing signal (L1sync).

In some embodiments, counter 202 can, in addition and/or in thealternative, be configured to reset to a zero count (e.g., if a risingor falling edge of the reset signal is detected or if the reset signalis in a low state) or to continue counting (e.g., if the reset signal isnot at a rising/falling edge or the reset signal in a high state) basedon the particular state of the reset signal. The same (state of the)reset signal (waveform 214) is provided to each chip of the plurality ofIC chips 100. The same (state of the) reference clock signal (waveform210) is also provided to each chip of the plurality of IC chips 100. Thetiming signal (waveform 216) is provided to all chips of the pluralityof IC chips 100 via the daisy chain arrangement described above. Thesame timing signal (or state of the timing signal) is received by all ofthe chips 100 within a single period of the reference clock signal.

For example, the rising edge of waveform 214 (reset signal) shown inFIG. 2B specifies to the counter 202 to reset its counter. The risingedge or a high state of waveform 216 (timing signal) (e.g., portion 218of waveform 216) is configured to occur and be received by all of thechips 100 within a same single period (e.g., period 222) of waveform 212(converted reference clock signal). Portion 218 of waveform 216comprises the trigger or identification of a particular time point fromwhich the counter 202 is to start counting. Portion 218 is configurednot to violate any set up and/or hold constraints associated with thechip. Accordingly, detection of the particular period 222 of theconverted reference clock signal causes counter 202 to increment by oneso that the count now equals one. Alternatively, the period immediatelyafter the particular period 222 may cause counter 202 to increment by 1so that the count now equals one. In any case, all of the chips 100 areconfigured to conform to the same counter increment triggeringconvention. Counter 202 continues to increment with each successivecycle/period of the converted reference clock signal until a particularchange to the reset signal is detected.

A counter included in each of the remaining chips 100 simultaneouslyperforms the same counting function based on the same input signals.Thus, the first level reference time signals outputted by the countersof all of the chips 100 specify the same count value at each time point.The first level (L1) counters are synchronized between the chips of theplurality of IC chips 100. The same count value specified by the firstlevel reference time signals across all of the chips 100 can be used asa common or synchronized reference time for the chips 100 to synchronizeor simultaneously perform one or more particular operations/actions inmore than one chip of the plurality of IC chips 100. For instance, whenthe first level reference time signal is at a count of 5,000, a firstparticular operation is to be performed in each chip of the plurality ofIC chips 100; when the first level reference time signal is at a countof 10,005, a second particular operation is to be performed by chip 1,chip 2, and chip 40; when the first level reference time signal is at acount of 50,500, a third particular operation is to be performed by allof chips 100; and the like.

FIG. 3 is an example illustration of a block diagram showing generationof a second level reference time in a chip in accordance with someembodiments of the present disclosure. In some embodiments, each of thechips 100 can include circuitry/components such as circuitry 105associated with distribution of the timing signal L1sync in the daisychain arrangement and a section 300 to generate a second level referencetime signal. Section 300 can comprise section 113, 115, or 117 ofFIG. 1. The second level reference time signal is also referred to as anL2 reference time, a L2 reference timing signal, or the like. The secondlevel reference time signal comprises a higher resolution reference timebased on the first level reference time signal. Thus, the first levelreference time signal may be considered to be a coarse (resolution)reference time and the second level reference time signal may beconsidered to a fine or (higher resolution) reference time.

Section 300 is configured to generate and output the second levelreference time signal (L2_reference_time) based on the timing signal(L1sync) and the reference clock signal (sinus_refclk). In section 300,subsection 301, first level counter 302, and amplifier/buffer 304 aresimilar to respective subsection 200, counter 202, and amplifier/buffer204 of FIG. 2A. Timing signal (L1sync) is an input to the first levelcounter 302. The converted reference clock signal (refclk) generated byamplifier/buffer 304 comprises an input to each of the first levelcounter 302 and flip flop 308. The first level reference time signal(L1_reference_time) and output of a second level register 305 comprisethe inputs to a comparator 306. The second level register 305, alsoreferred to as a L2_time_start register, is configured to store orspecify a particular first level reference time signal count value(e.g., a pre-defined count value) associated with triggering actuationof a second level counter 314.

Comparator 306 is configured to determine if the count value specifiedby the first level reference time signal at least equals (is equal to orgreater than) the pre-defined count value specified in the second levelregister 305. Flip flops 308 and 312 provided at the output of thecomparator 306 are configured to generate a second level reference timestart signal (L2sync) in accordance with the determination made by thecomparator 306. If the comparator 306 determines that the two countvalues are at least equal to each other, then the second level referencetime start signal is configured to have a rising edge without delay, tospecify a trigger similar to portion 218 shown in FIG. 2B but fortriggering start of counting by the second level counter 314. If thecomparator 306 determines that the two count values are not at leastequal to each other (that the first level reference time signal countvalue is less than the second level register 305 pre-defined countvalue), then the second level reference time start signal is configuredto not include a rising edge. The second level reference time startsignal is analogous to the timing signal L1sync for the first levelcounter 302 or 202 but instead for the second level counter 314. Thesecond level reference time start signal is also referred to as a startsignal, a second level timing signal, L2sync, and/or the like.

In some embodiments, flip flop 308 may be configured to generate aninitial signal with a rising edge in accordance with the determinationmade by the comparator 306, and flip flops 312 may be configured todetect the rising edge included in the initial signal and generate afinal signal indicative of the detected rising edge to the second levelcounter 314. The final signal to the second level counter 314 comprisesthe start signal, L2sync signal, and/or second level reference timestart signal. The first pulse of the start signal starts or triggers thesecond level counter 314.

Another input to the second level counter 314 comprises a referencedigital clock signal (clk_dbf) from a reference clock phase lock loop(CLK PLL) 316. In some embodiments, this digital clock signal (clk_dbf)comprises a sinusoidal waveform having a frequency of N times that ofthe reference clock signal (sinus_refclk). Digital clock signal(clk_dbf) is analogous to reference clock signal (sinus_refclk) inputtedto the first level counter 302/202, except due to its higher frequency,the period or cycle of digital clock signal (clk_dbf) is smaller thanthat of the reference clock signal (sinus_refclk) and thereby provides abetter time resolution. The smaller periodicity of digital clock signal(clk_dbf), in turn, permits finer/smaller time resolution counting thanassociated with L1_reference_time and the first level counter 202/302alone. Digital clock signal (clk_dbf) from CLK PLL 316 is also an inputto the flip flops 312 to facilitate generation of L2sync to reset orresynchronize the second level counters in all of the chips 100.

Second level counter 314, also referred to as a L2_time_counter, isconfigured to start counting the number of periods or cycles of thedigital clock signal (clk_dbf) starting from a trigger or start timepoint specified by the second level reference time start signal. In someembodiments, a rising edge detection in the first pulse of the secondlevel reference time start signal (L2sync) comprises the trigger orstart of counting by the second level counter 314. The output of thesecond level counter 314 comprises the second level reference timingsignal (L2_reference_time), which specifies the present or real-timecount value. Once the second level counter 314 starts counting, thecounter is free running and the next pulses of the second levelreference time start signal do not reset or reinitialize the counteruntil another trigger from flip flop 308 is issued.

In an embodiment, without limitation, the second level reference timingsignal (L2_reference_time) may comprise 32 bits, and may be stored inmemory locations [31:0]. As an example, the second level referencetiming signal (L2_reference_time) can be used to synchronize data reador write buffers or registers located in more than one chip of theplurality of IC chips 100 or otherwise synchronize performance ofparticular operations/actions at particular clock cycles across thechips 100.

FIG. 4A is an example illustration of a block diagram showing generationof a modified second level reference time in a chip in accordance withsome embodiments of the present disclosure. In some embodiments, each ofthe chips 100 can include circuitry/components such as circuitry 105associated with distribution of the timing signal L1sync in the daisychain arrangement and a section 400 to generate a modified second levelreference time signal. Section 400 can comprise section 113, 115, or 117of FIG. 1. The modified second level reference time signal is alsoreferred to as a modified L2_reference_time, a modified L2 referencetiming signal, a L2′_reference_time, a L2′ reference timing signal, orthe like. The modified second level reference time signal comprises ahigher resolution reference time based on the first level reference timesignal. Thus, the first level reference time signal may be considered tobe a coarse (resolution) reference time and the modified second levelreference time signal may be considered to a fine or (higher resolution)reference time.

In some embodiments, the count resolution per time offered by themodified second level reference time is the same as with the secondlevel reference time. The second level reference time may be referred toas a first level L2_reference_time and the modified second levelreference time may be referred to as a second level L2_reference_time.Second level reference time or modified second level reference time maybe generally referred to as L2 time.

In some embodiments, the second level reference time signal outputted bysecond level counter 314 may not be ideal for use in a differentfrequency environment associated with at least a portion of a chip. Thesecond level reference time signal is based on a different frequencyclock signal (clk_dbf) than the frequency environment associated withthe at least a portion of the chip (e.g., the frequency associated withthe clock signal used within the at least portion of the chip). Alatency mismatch of the clock trees associated with the respectivedifferent frequencies can occur. The modified second level referencetime generated in section 400 has a resolution, for example, that isfour times better than the period of the clock signal (clk_dbf). This isachieved by controlling the initial phase of the clock signal (clk_dbf)applied to the modified second level counter 418 without the need forthe clock signal (clk_dbf) to be at a higher frequency than it is.Section 400 may be implemented instead of section 300 in such a chip toretain the higher resolution possible with the second level time signalwithout latency mismatch.

Section 400 is configured to output the modified second level referencetime signal based on the timing signal (L1sync) and the reference clocksignal (sinus_refclk). In section 400, a subsection 401, first levelcounter 402, amplifier/buffer 404, second level register 405, comparator406, and flip flop 408 are similar to respective subsection 301, firstlevel counter 302, amplifier/buffer 304, second level register 305,comparator 306, and flip flop 308 of FIG. 3.

In some embodiments, converted reference clock signal (refclk) generatedby amplifier/buffer 404 comprises the input to a clock tree 422. Theclock tree 422, also referred to as a low latency clock tree, comprisesa plurality of flip flops. Clock tree 422 is configured to split theconverted reference clock signal (refclk) into a plurality of splitsignals, in which each signal of the plurality of split signalscomprises a signal phase shifted by a certain amount. Split signals areprovided to various components included in a subsection 410 such as, butnot limited to, the first level counter 402 and flip flop 408.

First level counter 402, second level register 405, comparator 406, flipflop 408, and associated flip flops included in subsection 410 may bephysically located proximate to each other to reduce clock tree latency.

A start signal (L2sync) outputted from flip flops 408, 412 is similar tothe start signal outputted from flip flops 308, 312. The start signal(L2sync) comprises an input to a phase selection and clock generator414.

A CLK PLL 416 is configured to generate a digital clock signal (clk_dbf)having, for example, a frequency of N times the frequency of thereference clock (sinus_refclk). CLK PLL 416 is similar to CLK PLL 316.The digital clock signal (clk_dbf) from CLK PLL 416 comprises the inputto a clock tree 426. Clock tree 426, also referred to as a low latencyclock tree, comprises a plurality of flip flops configured to split theinput signal into a plurality of split signals to provide to flip flops412 and generator 414 with low latency. Clock tree 426 may be similar toclock tree 422. In some embodiments, flip flops 412 and generator 414are physically located proximate to each other to reduce clock treelatency.

Another input to generator 414 comprises selectable phase(s) from aphase selection register or similar component. The phase(s) is selectedbased on 360/N, where the resolution of phase selection is based onN*frequency of the clock signal (clk_dbf). This means the modifiedsecond level counter 418 can start counting with a resolution N timeshigher than the period of the clock signal (clk_dbf). Generator 414 isconfigured to generate the new digital clock signal in the samereference clock domain as the chip (or chip portion) in which the clocksignal counts is to be used in accordance with the digital clock signal(clk_dbf) and selected phase(s). Generator 414 is configured to generatea new digital clock signal having a frequency which is the same as theclock signal (clk_dbf), but the phase can be programmed with aresolution that is N times better or higher. Generator 414 comprises amulti-phase programmable divider. Generator 414 may also be referred toas a phase selection and clock generation module.

For instance, the phase selection in generator 414 may be a 1080 MHzclock signal, while the reference clock domain of the chip (or chipportion) of interest is a 270 MHz environment (e.g., the reference clockof the chip/system clocks in at 270 MHz). A phase selection of 90 degreeincrements (or phase selections of 90, 180, 270, and 360 degrees) of1080 MHz is inputted to generator 414. In response, the generator 414generates a new digital clock signal at 270 MHz, corresponding to one ofthe four selected phases of 1080 MHz. The 270 MHz frequency of the newdigital clock signal has the correct phase to be used as the digitalclock of the chip (or chip portion) of interest.

The output of generator 414 comprises the input to a clock tree 424.Clock tree 424 comprises a high latency clock tree having a greaternumber of flip flops than either of clock trees 422 or 426. Clock trees426 and 422, by contrast, each comprises a low latency clock tree havinga relatively small number of flip flops. Clock tree 424 is configured togenerate a plurality of split signals (e.g., four split signals) basedon new digital clock signal generated by generator 414.

The split signal(s) comprise the input to the modified second levelcounter 418. Modified second level counter 418 is configured toduplicate the fine count resolution capability of the second levelcounter 314, except the output of modified second level counter 418comprises a modified second level reference time signal that isconfigured for use in the digital clock domain of the chip (or chipportion) of interest. The modified second level counter 418 is clockedby the new digital clock signal and generates the modified second levelreference time signal that is indicative of sub-periods or phaseincrements of the new digital clock signal in accordance with the phaseselection inputted to the generator 414.

Continuing the above example, the counter 418 increments by one for eachsuccessive 90 degree phase of the new digital clock signal, for a totalof four counts per period of the new digital clock signal. In contrast,the second level counter 314 is clocked by the digital clock signal(clk_dbf) and the count increments by one for each period of the digitalclock signal (clk_dbf). Modified second level counter 418 is alsoreferred to an L2_time_counter or a second level L2_time_counter.

In an embodiment, the modified second level reference time signalcomprises a count value that is the same as would be for the secondlevel reference time signal outputted from counter 314. FIG. 4Billustrates example clock signals in accordance with some embodiments ofthe present disclosure. Clock signals 450 and 454 represent clock orreference signals associated with different frequency clock domains orenvironments. In FIG. 4B, clock signal 454 has a frequency that is 4times greater than that of clock signal 450. Within the time duration ofa single period 452 of clock signal 450, four periods 456, 457, 458, and459 of clock signal 454 occur. In other words, for every 90 degree phase(e.g., ¼ period) of clock signal 450, a single period or cycle of clocksignal 454 occurs. Counting each period/cycle of clock signal 454 isequivalent to counting each successive 90 degree phase or ¼ periodportion of clock signal 450.

Accordingly, if clock signal 450 is counted in 90 degree phase or ¼period increments (instead of by each full period or cycle), then thecount value associated with clock signal 450 can be the same as thecount value associated with clock signal 454. Such count valueassociated with clock signal 450 is at a higher resolution than theperiodicity of clock signal 450. Each period of clock signal 450increments the counter by more than one (e.g., counter increments byfour). For sub-period counting scheme, clock signal 454 can be used andpermits the count value to be used in an environment where clock signal450 comprises the clocking or reference signal and/or where, in the sameenvironment, a higher or finer resolution count than the periodicity ofclock signal 450 may be required to perform certain actions.

As an example, without limitation, clock signal 450 may be an example ofthe new digital clock signal generated by generator 414 and clock signal454 may be an example of the higher frequency clock signal (clk_dbf)from CLK PLL 416. The modified second level counter 418 is configured toprovide an initial phase with a resolution that is smaller or finer thana period of the new digital clock signal.

It is understood that the sub-period phase accuracy scheme describedabove can be implemented in less or greater than four phases per period.For instance, without limitation, generator 414, phase selectionregister, and/or clock tree 424 can be configured so that each 45 degreephase of the signal outputted by generator 414 increments the count incounter 418, for a total of eight counts per signal period.

The modified second level reference time signal outputted by themodified second level counter 418 is used to synchronize and/or sequencecertain actions in certain components/logic 420 included in chip(s).

FIG. 4C illustrates a block diagram showing an example use of the firstlevel reference time signal, second level reference time signal, ormodified second level reference time signal in accordance with someembodiments of the present disclosure. Counter 460 comprises any ofcounters 202, 314, or 418 which provides the first level reference timesignal, second level reference time signal, or modified second levelreference time signal, respectively. A plurality of chip/circuit blocksis associated with a plurality of trigger indices sets. In particular,chip/circuit blocks 464, 474, and 484 of the plurality of chip/circuitblocks are associated with respective look up tables (LUTs) 462, 472,and 482 of the plurality of LUTs. Chip/circuit blocks 464, 474, and 484are examples of component/chip logic 420.

Each chip/circuit block of the plurality of chip/circuit blockscomprises at least a portion of a chip, circuit, or component.Chip/circuit blocks 464, 474, and 484 can be the same or different fromeach other. Chip/circuit blocks 464, 474, and 484 can be included in thesame chip or in more than one chip. Each LUT of the plurality of LUTsmaintains one or more pre-defined trigger indices, each trigger indexdefining a particular count value at which a particular action is to betaken by a particular chip/circuit block or a portion thereof. Thetrigger indices between LUTs can be the same or different from eachother. LUTs 464, 474, and/or 484 can be the same or different from eachother. In FIG. 4C, LUT 462 includes trigger indices 1, 2, 3, etc.; LUT472 includes trigger indices A, B, C, etc.; and LUT 482 includes triggerindices 1′, 2′, 3′, etc. Trigger indices 1, 2, 3, etc. included in LUT462 comprise, at a minimum, all the trigger indices relevant foroperation of chip/circuit block 464. Trigger indices A, B, C, etc. andtrigger indices 1′, 2′, 3′, etc. are likewise included as relevant forrespective chip/circuit blocks 474, 484.

In some embodiments, the current count value from counter 460 (e.g., thefirst, second, or modified second level reference time signal) isprovided to each of LUTs 462, 472, and 482. In response, each LUT (orassociated processor component) determines whether the current countvalue is equal to a pre-defined count value associated with any of thetrigger indices it maintains. If the current count value is equal to apre-defined count value, then the chip/circuit block or portion thereofassociated with that triggered index is actuated or otherwise commandedto perform a particular action. As an example, trigger index 1 of LUT462 may specify triggering a write operation to register A inchip/circuit block 464 at a count value of 1000. If the current countvalue is 1000, then trigger index 1 would be triggered and the writeoperation to register A takes place.

In some embodiments, the trigger indices can be provided in a formatother than in LUTs; LUTs 462, 472, and 482 may be combined into a singleLUT; and/or the like.

FIG. 5 is an example illustration of an IC chip 500 included in theplurality of IC chips 100 in accordance with some embodiments of thepresent disclosure. Chip 500 comprises, for example, a digitalbeamformer (DBF) chip. Chip 500 includes, without limitation, a timesynchronization section 502, a transmit section 504, a receive section506, and a section to distribute the L1sync signal similar to section105 (not shown). Section 504 and/or 506 (or a portion thereof) comprisesan example of the components/logic 420.

Time synchronization section 502 comprises one of sections 208, 300, or400. Time synchronization section 502 receives as inputs the referenceclock signal from the reference clock 110 and the timing signal L1syncfrom the proceeding chip in the daisy chain arrangement (or modem 108 ifchip 500 is the first chip in the daisy chain arrangement). Transmitsection 504 is configured to receive data beam(s) from the modem 108 andconfigure the data beam(s) into a format suitable for transmission by aplurality of antenna elements 508. Transmit section 504 includes adigital baseband processing section 510 and a plurality of radiofrequency (RF) processing sections 516.

Each of the sections 510 and 516, in turn, includes a plurality ofelectrical components or logic, one or more of which may be synchronizedin operation between chips in the daisy chain arrangement via use of thefirst level, second level, or modified second level reference timesignal (depending on particular reference time signal produced bysection 502). For example, a time delay filter 512, plurality of phaseshifters 514, DACs 518, and/or the like included in section 504 may beactuated or cause to perform its respective functions at particularcount values of the reference time signal. The same components/logic inother chips of the plurality of IC chips 100 are actuated or caused toperform its functions at the same particular count values as in chip 500via use of the respective reference time signals in the other chips.

Receive section 506 is configured to receive RF signals from theplurality of antenna elements 508 and process the RF signals to recoverthe underlying data beam(s) to provide to modem 108. Receive section 506includes a digital baseband processing section 530 and a plurality of RFprocessing sections 536. Each of the sections 530 and 536, in turn,includes a plurality of electrical components or logic, one or more ofwhich may be synchronized in operation between chips in the daisy chainarrangement via use of the first level, second level, or modified secondlevel reference time signal (depending on particular reference timesignal produced by section 502). For example, a time delay filter 532,plurality of phase shifters 534, analog-to-digital converters (ADCs)538, and/or the like included in section 506 may be actuated or cause toperform its respective functions at particular count values of thereference time signal. The same components/logic in other chips of theplurality of IC chips 100 are actuated or caused to perform itsfunctions at the same particular count values as in chip 500 via use ofthe respective reference time signals in the other chips.

In some embodiments, only one of sections 504 or 506 may be included inchip 500. The transmitter associated components can be implemented inthe same or different chip as the chip including the receiver associatedcomponents.

Other examples of use of L2 time include, without limitation,synchronization and/or sequencing of operations involving DBFs, DACfirst in first outs (FIFOs), calibration, and/or the like.

FIG. 6 is an example illustration of a top view of an antenna lattice600 in accordance with some embodiments of the present disclosure.Antenna lattice 600 (also referred to as a phased array antenna)includes a plurality of antenna elements 602 arranged in a particularpattern to define a particular antenna aperture. The antenna aperture isthe area through which power is radiated by or to the antenna elements602. A phased array antenna synthesizes a specified electric field(phase and amplitude) across an aperture. Adding a phase shift to thesignal received or transmitted by each antenna in an array of antennasallows the collective signal of these individual antennas to act as thesignal of a single antenna.

A subset 604 of the plurality of antenna elements 602 can comprise the Mantenna elements 508 associated with chip 500 and a subset 606 of theplurality of antenna elements 602 can comprise the M antenna elementsassociated with another chip of the plurality of IC chips 100. Theremaining subsets of antenna elements of the plurality of antennaelements 602 may be similarly associated with the remaining chips of theplurality of IC chips 100.

In some embodiments, 50, 100, or more chips comprising the plurality ofIC chips 100 may be distributed over a printed circuit board (PCB) thatis 0.5 meter (m), 1 m, greater than 1 m in size, or the like. The timingsignals generated by the chips 100 (e.g., the first level reference timesignals, second level reference time signals, or modified second levelreference time signals) permit time synchronization of operations in thechips 100 to be performed within less than a few tenth of a picosecond(ps), less than a few hundred ps, or the like of each other. The timingsignals generated by the chips 100 (e.g., the first level reference timesignals, second level reference time signals, or modified second levelreference time signals) permit time synchronization of operations in thechips 100 to be performed at a higher accuracy of each other than withuse of the chips' input reference clock signal (e.g., reference clocksignal (sinus_refclk) from reference clock 110).

Time delay filter 512 in chip 500 and time delay filters in transmitsections of other chips in the daisy chain arrangement may, for example,be actuated or caused to perform encoding time delay to the receiveddata beams at 10,000 count value of the respective reference timesignals. The plurality of phase shifters 514 in chip 500 and phaseshifters in transmit sections of other chips in the daisy chainarrangement may, for example, by actuated or caused to perform encodingof phases to the received data beams at 14,700 count value of therespective reference time signals. The time synchronization schemedisclosed herein allows dynamic control of the plurality of chips 100,especially control of time sensitive operations or actions in the chips100 by linking/triggering particular operations/actions across the chips100 to particular reference time signals. Each chip of the chips 100generates and maintains a same reference time signal.

In this manner, RF signals to be transmitted will be provided at thesame time to the plurality of antenna elements 508 for simultaneoustransmission. RF signals to be transmitted will also be provided torespective subsets of plurality of antenna elements for the remainingchips so that all the antenna elements of the antenna lattice transmitor radiate at the same time.

In some embodiments, the chips of the plurality of IC chips 100 may bethe same or different from each other. For example, without limitation,chip 1 may be a processor chip, chip 2 may be a DBF chip, chip 3 may bean amplifier chip, chip 4 may be memory chip, and the like. Each ofthese chips can include section 105 and one of sections 208, 300, or 400so as to synchronize or simultaneously perform particularoperations/actions at particular times.

FIG. 7 is an example illustration of a block diagram showing circuitryor component section 700 associated with a RF PLL synchronization schemein accordance with some embodiments of the present disclosure. In someembodiments, each of the IC chips 100 can include circuitry/componentssuch as circuitry 105 associated with distribution of the timing signalL1sync in the daisy chain arrangement and section 700 configured toprovide RF PLL synchronization between the IC chips 100 as described indetail herein.

In some embodiments, section 700 includes a reference time generator702, a RF PLL register 704, a comparator 706, a state machine 708, asynchronization trigger register 710, flip flops 712, a RF module 714,and a clock tree 730. The reference time generator 702 is configured tooutput a reference time signal, which is an input to the comparator 706.The output of the RF PLL register 704 also comprises an input to thecomparator 706. The output of the comparator 706 comprises the input tothe state machine 708. The output of the synchronization triggerregister 710 is also an input to the state machine 708. The flip flops712 are electrically coupled between the state machine 708 and the RFmodule 714. The clock tree 730 is electrically coupled between thereference time generator 702 and RF module 714.

In some embodiments, reference time generator 702 comprises one ofsections 208, 300, or 400, and correspondingly, the reference timesignal outputted by reference time generator 702 comprises respectiveone of the first level, second level, or modified second level referencetime signal. Alternatively, reference time generator 702 can compriseany of a variety of reference time generators capable of generating areference time signal of sufficient count resolution to be able tofacilitate performance of the RF PLL synchronization disclosed herein.

The RF PLL register 704 is configured to store, specify, or define aparticular reference time signal count value (e.g., a pre-defined countvalue) associated with resetting a sigma delta modulator (SDM) includedin a RF PLL 718 of the RF module 714. RF PLL register 704 is alsoreferred to as an Lx_RF_PLL register. If the reference time signalcomprises the first level reference time signal (L1_reference_time),then the particular reference time signal count value stored in the RFPLL register 704 comprises a particular first level reference timesignal count value (L1_RF_PLL). If the reference time signal comprisesthe second level reference time signal (L2_reference_time), then theparticular reference time signal count value stored in the RF PLLregister 704 comprises a particular second level reference time signalcount value (L2_RF_PLL). Likewise, if the reference time signalcomprises the modified second level reference time signal (modifiedL2_reference_time), then the particular reference time signal countvalue stored in the RF PLL register 704 comprises a particular modifiedsecond level reference time signal count value (modified L2_RF_PLL).

In some embodiments, RF PLL 718 included in RF module 714 as well as theRF PLLs included in each of the remaining IC chips 100 are started andonce they have reached a locked state (e.g., have reached a steadyoperational state), a synchronization between the RF PLLs in theplurality of IC chips 100 can occur. The synchronization request isinitiated via an update to a slave interface or synchronization triggersignal. The readiness of the RF PLLs of the IC chips 100 to besynchronized can be indicated by a particular value of thesynchronization trigger register 710. As an example, the register valueof register 710 can transition from a “0” to a “1” in accordance withthe synchronization request.

Comparator 706 is configured to determine if the reference time signalequals the pre-defined count value stored in the RF PLL register 704.The output of the comparison is provided to the state machine 708. Thestate machine 708 is configured to receive the value of thesynchronization trigger register 710, also referred to as a controlregister. If the reference time signal equals the pre-defined countvalue of the RF PLL register 704 and the value of the synchronizationtrigger register 710 is indicative of a synchronization request orreadiness, then the state machine 708 is configured to generate andprovide a particular signal to the RF PLL 718 via the flip flops 712.The particular signal provided to the RF PLL 718 can be any signal thatis recognized by the RF PLL 718 as the command to performsynchronization. In some embodiments, without limitation, the particularsignal comprises a four refclk clock cycle pulse (e.g., a signal highcomprising a pulse width of four periods of the reference clock signalgenerated by the reference clock 110). Such particular signal is alsoreferred to as an LxSYNC signal, an Lx time synchronization signal, anLx time digital synchronization reset, a sync input signal, and/or thelike. If both conditions are not met, the state machine 708 isconfigured to provide no signal or a signal that is not the particularsignal to RF PLL 718.

A state machine included in each of the remaining IC chips 100 issimilarly configured to provide a particular signal to the respective RFPLL included in each of the remaining IC chips 100. All the RF PLLs inthe IC chips 100 can be simultaneously synchronized using particularsignals in the IC chips 100 that are generated at the same time inaccordance with the same reference time signal. In some embodiments,flip flops 712 comprise one or more flip flops configured to reducelatency of providing the particular signal to RF PLL 718, to facilitategeneration of the particular signal, and/or to facilitate providing theparticular signal to RF PLL 718 in synchronicity with the RF PLLs in theremaining IC chips 100.

RF module 714 includes a signal processing unit 716, the RF PLL 718, anda transmit section 720. The signal processing unit 716 is configured toreceive the reference clock signal (sinus_refclk) from the referenceclock 110 and to process the signal into a format usable by othercircuits/components of section 700. Among other things, signalprocessing unit 716 can convert the reference clock signal(sinus_refclk), which comprises a sinusoidal waveform shape, into theconverted reference clock signal (refclk) having a square waveformshape. The converted reference clock signal (refclk) can be provided,without limitation, to each of the clock tree 730 and RF PLL 718.

RF PLL 718 is electrically coupled to the transmit section 720. Transmitsection 720 includes baseband processing and RF processing subsectionsassociated with encoding one or more data signals for RF transmission.Transmit section 720 includes, among other things, a plurality of phaseshifters 722 to facilitate signal encoding and/or beamforming. Transmitsection 720 can be similar to transmit section 504. The particularsignal to the RF PLL 718 from the state machine 708 is used tosynchronize the phases of the RF PLL 718. Similar reference time signalsynchronizes phase shifters 722 with the phases of the phase shifters inthe other IC chips 100. Accordingly, even though a distributed PLLscheme is implemented in the plurality of IC chips 100, precise phasesynchronization between the phase shifters in the plurality of IC chips100 is possible.

The converted reference clock signal (refclk) is provided to each of thestate machine 708 and reference time generator 702 via the clock tree730. Clock tree 730 is configured to reduce latency in the provision ofthe converted reference clock signal (refclk) to its intendedrecipients.

FIG. 8 is an example illustration of a block diagram showing circuitryor electrical components included in the RF PLL 718 in accordance withsome embodiments of the present disclosure. In some embodiments, RF PLL718 includes a reference divider/multiplier 800, a phase detector 802, aloop filter 804, a voltage controlled oscillator (VCO) 806, a frequencydivider 808, and a sigma delta modulator (SDM) 810. The input to the RFPLL 718 is received by the reference divider/multiplier 800. The phasedetector 802 is electrically coupled between the referencedivider/multiplier 800 and the loop filter 804. The loop filter 804 iselectrically coupled between the phase detector 802 and VCO 806. Theoutput of VCO 806 comprises the output of the RF PLL 718 and alsocomprises an input to the phase detector 802 via the frequency divider808. A first feedback loop is thereby formed comprising the phasedetector 802, loop filter 804, VCO 806, and frequency divider 808. Theoutput of frequency divider 808 comprises the input to SDM 810. Theoutput of SDM 810 comprises the input to frequency divider 808.Frequency divider 808 also generates the clock for the SDM 810.

RF PLL 718 is configured to be an integer-N PLL and/or a fractional-NPLL. Depending on the parameters associated with frequency divider 808and SDM 810, the frequency of the output signal of RF PLL 718 comprisesan integer multiple or a non-integer multiple of the frequency of theinput signal. Reference divider/multiplier 800 is configured to apply acertain divider or multiplier value to the input signal so as to obtaina reference signal. The phase detector 802 is configured to detectdifferences in the phase associated with the reference signal (the firstsignal) and the phase associated with the output of VCO 806 with thefrequency divider ratio applied in accordance with frequency divider 808(the second signal), and generates a (voltage) signal in accordance withthe phase difference between the two signals. The phase detector 802 isalso referred to as a phase comparator.

Loop filter 804 is configured to filter the output from the phasedetector 802 to facilitate maintaining RF PLL stability. VCO 806 isconfigured to oscillate at a higher frequency than the reference signal.VCO 806 is tunable over an operational frequency band associated withthe loop. The output of the loop filter 804 (e.g., the filtered errorsignal indicative of the phase difference) is applied to VCO 806 as thetuning voltage of VCO 806. The frequency associated with the outputsignal of VCO 806 is tuned or defined in accordance with the output ofthe loop filter 804.

Frequency divider 808 is configured to change the frequency of thesignal from VCO 806 using a divider ratio selected via the SDM 810. Thedivider ratio N, also referred to as the divider or ratio, is applied as1/N or ±N to the signal from VCO 806 to generate a signal having afrequency that is the frequency of the signal from VCO 806 divided by N.Such frequency divided signal comprises the second signal received byphase detector 802.

If the output of VCO 806 comprises N times the frequency of the inputsignal, then the frequency divider 808 has a ratio of 1/N, near 1/N, orother ratio at that point in time. The divider ratio of the frequencydivider 808 can change over time in accordance with the SDM 810. Thedivider ratio of frequency divider 808 can vary over time just so longas the average frequency of the output signal over time is the desiredfrequency of the output signal.

Initially, the RF PLL 718 will be out of lock as the first and secondsignals will not be the same. When the two signals become equal in phaseand frequency over time, the error signal (the output of phase detector802) will be constant and the RF PLL 718 is considered to be in a lockedstate. When all the RF PLLs in the plurality of IC chips 100 are in alocked state, register 710 in each of the IC chips 100 transitions to avalue indicative of the readiness of the RF PLLs for synchronization.

FIG. 9 is an example illustration of a block diagram showing additionalcircuitry or component details of the RF PLL 718 in accordance with someembodiments of the present disclosure. In some embodiments, frequencydivider 808 includes a plurality of modulators such as modulators 900,902, 904, and 906. Each of modulators 900-906 is configured to select aparticular divider value under control by the SDM 810. Modulator 902 iselectrically coupled between modulators 900 and 904. Modulator 904 iselectrically coupled between modulators 902 and 906. SDM 810 iselectrically coupled to each of modulators 900-906. Modulators 900-906is also referred to as selective divider modulator, divider modulators,and/or the like.

Each of modulators 900, 902, and 904 comprises divider I or I+1 (denotedas I/I+1), where I is an integer. Modulator 906 comprises an integerdivider between P to Q (denoted as P:1:Q), where P and Q are integers,P<Q, and I or I+1 can equal P. This combination is an example and othercombinations of integer dividers can be also used. SDM 810 comprises asigma-delta random number generator or sequence configured to specifythe configuration of modulators 900-906 so as to define the dividerratio of the feedback divider 808 to apply in the first feedback loop.The sigma-delta sequence maps to selection of particular divider valuesin modulators 900-906. The modulator sequence of modulators 900-906comprises the divider ratio of the feedback divider 808. The dividerratio can range between I*I*I*P to (I+1)*(I+1)*(I+1)*Q. The modulatorsequence of the feedback divider 808 changes as the sigma-delta sequenceof the SDM 810 changes.

For instance, divider I is selected in modulator 900, divider I isselected in modulator 902, divider I+1 is selected in modulator 904, anddivider P+2 is selected in modulator 906 in accordance with the SDM 810.The modulator sequence thus defined is a divider ratio value equal toI*I*(I+1)*(P+2).

The modulator sequence of the feedback divider 808 changes as thesigma-delta sequence of the SDM 810 changes over time. The divider ratioat a given moment in time need not equal the desired divider ratio aslong as the average divider ratio over a given time equals the desireddivider ratio. The divider ratio at any given moment in time can be aninteger value while the average divider ratio is a non-integer value. Asan example, assume the desired divider ratio is 10.1 (a fractional modevalue). In 1000 cycles of the first feedback loop, 90% of the dividerratio of feedback divider 808 is 10 and in the remaining 10% of the 1000cycles, the divider ratio is 11. The average divider ratio over the 1000cycles is 10.1=0.9*10+0.1*11.

In some embodiments, a synchronization unit 908 electrically coupled toSDM 810 is configured to receive signals associated with operation ofSDM 810. Alternatively, synchronization unit 908 can be included in SDM810. Examples of signals received by synchronization unit 908 include,without limitation, a SDON signal 910 to control the on and off statesof SDM 810, the LxSYNC signal 912 to initiate synchronization of SDM810, and a LxSYNCEN signal 914 to effect synchronization of SDM 810 whenin fractional mode. The SDON signal 910 can be set to “0” or “1” to haveSDM 810 in the off or on state, respectively. The LxSYNC signal 912comprises the particular signal generated by the state machine 708 ifboth conditions are met. As shown in FIG. 9, LxSYNC signal 912 comprisesa pulse that is four refclk clock cycles or period wide. The LxSYNCENsignal 914 comprises an enable bit control signal that transitions froma low to a high prior to the LxSYNC signal 912. In some embodiments,both the LxSYNC signal 912 and LxSYNCEN signal 914 are enabled for SDM810 synchronization to occur in fractional mode. The LxSYNC signal 912alone is sufficient to initiate synchronization of SDM 810 in integermode. Alternatively, the LxSYNC signal 912 is sufficient to initiatesynchronization for fractional and integer modes of RF PLL 718.

Accordingly, the SDM of the RF PLL included in each chip of the IC chips100 is synchronized to each other using the reference time signal. Thereference time signal generated in each of the IC chips 100 is highlysynchronized between the IC chips 100 as described above. Thus, thesynchronization of the SDMs occurs simultaneous or nearly simultaneouslyof each other. The synchronization causes all the SDMs of the RF PLLs inthe IC chips 100 to reset to the same point or value of the samesigma-delta sequence at the same (or near same) time so that, in turn,the same modulator sequence occurs in all the feedback dividers of theRF PLLs from that time onward. The same modulator sequence in all ICchips 100 results in setting the outputs of the RF PLLs across the ICchips 100 to the same frequency multiplier. In this manner, the RF PLLs,although distributed across the plurality of IC chips 100, perform insynchronicity with each other, enabling alignment of other chipfunctions such as the phases of the phase shifters between IC chips 100.

FIG. 10 is an example illustration of divider ratios over time in aplurality of IC chips 100 in accordance with some embodiments of thepresent disclosure. Plot 1000 shows the sequence of divider ratiosassociated with a first chip after implementation of the LxSYNC signal,and plot 1002 shows the sequence of divider ratios associated with asecond chip different from the first chip after implementation of theLxSYNC signal. Notice the synchrony or sameness of the divider ratiosbetween the first and second chips as a function of time following theSDM synchronization operation. Prior to synchronization, plots 1000 and1002 would be offset from each other along the time axis.

In this manner, the SDMs in the RF PLLs can be reset or synchronizedbetween the IC chips 100 using the same reference time signal generatedin each of the IC chips 100. The same reference time signals in the ICchips 100 is based on a same cycle of a common reference clock. In eachchip of the IC chips 100, a particular reference time count value atwhich the SDM is to be reset or synchronized is pre-set. The pre-setparticular reference time count value is the same in all the IC chips100. In each chip of the IC chips 100, the RF PLL is started andpermitted to continue running.

Once the RF PLL has achieved a locked state, a signal indicative of thelocked state or readiness for synchronization is provided to a componentincluded in the chip. In each chip of the IC chips 100, asynchronization trigger signal is generated (by the state machine) ifthe current reference time signal equals the pre-set particularreference time count value and there is a signal indicative of the RFPLL locked state/readiness of synchronization. The synchronizationtrigger signal comprises any signal recognized by the SDM as a triggerto initiate the reset or synchronization. As an example, withoutlimitation, the synchronization trigger signal can comprise a pulsehaving a pulse width comprising a particular multiple of the referenceclock cycle (e.g., a four refclk clock cycle pulse).

In response to the synchronization trigger, the same sigma-deltasequence included in each of the SDMs is reset or synchronized to thesame point or value. Henceforth, the RF PLLs in the IC chips 100 willhave the same divider ratio sequences and, by extension, the RF PLLswill also have the same frequency multiplier at its outputs. Prior tothe synchronization operation, different starting points of thesigma-delta sequence may occur within the SDMs at each given point intime, causing the corresponding divider ratio sequences in the feedbackdividers to be offset from each other.

In some embodiments, the plurality of IC chips 100 and the presentdisclosure herein can be included in a communications system, a wirelesscommunications system, a satellite-based communications system, aterrestrial-based communications system, a non-geostationary (NGO)satellite communications system, a low Earth orbit (LEO) satellitecommunications system, one or more communication nodes of acommunications system (e.g., satellites, user terminals associated withuser devices, gateways, repeaters, base stations, etc.), and/or thelike.

Examples of the devices, systems, and/or methods of various embodimentsare provided below. An embodiment of the devices, systems, and/ormethods can include any one or more, and any combination of, theexamples described below.

Example 1 is an apparatus including a first integrated circuit (IC) chipconfigured to receive a timing signal and a reference clock signal; asecond IC chip configured to receive the timing signal from the first ICchip and the reference clock signal; and a third IC chip configured toreceive the timing signal from the second IC chip and the referenceclock signal, wherein the second IC chip is electrically coupled betweenthe first and third IC chips, wherein the first, second, and third ICchips are configured to generate respective first, second, and thirdreference time signals based on the timing signal and the referenceclock signal, wherein the first, second, and third IC chips include arespective first, second, and third phase lock loop (PLL), and whereinthe first, second, and third PLLs are synchronized to each other basedon the respective first, second, and third reference time signals.

Example 2 includes the subject matter of Example 1, and further includeswherein the first, second, and third reference time signals aregenerated within a same first particular cycle of the reference clocksignal, wherein synchronization of the first, second, and third PLLs isinitiated during a same second particular cycle of the reference clocksignal, and wherein the first particular cycle of the reference clocksignal is a different cycle than the second particular cycle of thereference clock signal.

Example 3 includes the subject matter of any of Examples 1-2, andfurther includes wherein the first, second, and third PLLs includerespective first, second, and third sigma delta modulators (SDMs), andwherein the first, second, and third SDMs include a same sigma-deltasequence.

Example 4 includes the subject matter of any of Examples 1-3, andfurther includes wherein the first, second, and third PLLs compriseradio frequency (RF) PLLs, and wherein the first, second, and third PLLsinclude respective first, second, and third sigma delta modulators(SDMs).

Example 5 includes the subject matter of any of Examples 1-4, andfurther includes wherein the first, second, and third PLLs includerespective first, second, and third sigma delta modulators (SDMs) andrespective first, second, and third feedback dividers, and wherein thefirst, second, and third SDMs control a divider ratio associated withthe respective first, second, and third feedback dividers.

Example 6 includes the subject matter of any of Examples 1-5, andfurther includes wherein the first, second, and third PLLs includerespective first, second, and third sigma delta modulators (SDMs), andwherein synchronization of the first, second, and third PLLs comprisessynchronizing the first, second, and third SDMs to each other.

Example 7 includes the subject matter of any of Examples 1-6, andfurther includes wherein the first, second, and third PLLs includerespective first, second, and third sigma delta modulators (SDMs),wherein the first, second, and third SDMs include a same sigma-deltasequence, and wherein synchronization of the first, second, and thirdPLLs comprises synchronizing a starting point of the sigma-deltasequence in the first, second, and third SDMs to each other.

Example 8 includes the subject matter of any of Examples 1-7, andfurther includes wherein the first IC chip is configured to generate asynchronization signal to trigger phase synchronization of the first PLLto the second and third PLLs if the first reference time signal equals apre-set reference time signal count value and the first PLL is in alocked state.

Example 9 includes the subject matter of any of Examples 1-8, andfurther includes wherein the synchronization signal comprises a firstsynchronization signal, and wherein the second IC chip is configured togenerate a second synchronization signal to trigger phasesynchronization of the second PLL to the first and third PLLs if thesecond reference time signal equals the pre-set reference time signalcount value and the second PLL is in a locked state.

Example 10 includes the subject matter of any of Examples 1-9, andfurther includes wherein the first PLL includes a feedback dividerelectrically coupled to a sigma delta modulator (SDM), and wherein theSDM is configured to define a divider ratio sequence of the feedbackdivider.

Example 11 includes the subject matter of any of Examples 1-10, andfurther includes wherein the SDM includes a sigma-delta sequence, andwherein the divider ratio sequence is a function of the sigma-deltasequence.

Example 12 includes the subject matter of any of Examples 1-11, andfurther includes wherein the feedback divider comprises a plurality ofselective divider modulators, and wherein a first selective dividermodulator of the plurality of selective divider modulators is differentfrom a second selective divider modulator of the plurality of selectivedivider modulators.

Example 13 includes the subject matter of any of Examples 1-12, andfurther includes wherein each of the first, second, and third PLLscomprises one or both of an integer mode PLL or a fractional mode PLL.

Example 14 includes the subject matter of any of Examples 1-13, andfurther includes wherein at least two of the first, second, or third ICchips are identical to each other.

Example 15 includes the subject matter of any of Examples 1-14, andfurther includes wherein at least two of the first, second, or third ICchip are different from each other.

Example 16 includes the subject matter of any of Examples 1-15, andfurther includes wherein the first IC chip includes a clock phase lockloop (PLL) configured to generate and provide a second reference clocksignal at a higher frequency than the reference clock signal, whereinthe first IC chip is further configured to generate a fourth referencetime signal based on the first reference time signal and the secondreference clock signal, wherein the fourth reference time signalspecifies a count of a number of cycles of the second reference clocksignal starting from a particular cycle of the second reference clocksignal, and wherein the first PLL is synchronized based on the fourthreference time signal.

Example 17 includes the subject matter of any of Examples 1-16, andfurther includes wherein the fourth reference time signal has a finercount resolution than the first reference time signal within a same timeperiod.

Example 18 is an apparatus including a first integrated circuit (IC)chip including a first phase lock loop (PLL), wherein the first PLLincludes a first sigma delta modulator (SDM); a second IC chip includinga second PLL, wherein the second PLL includes a second SDM; a third ICchip including a third PLL, wherein the third PLL includes a third SDMand the second IC chip is electrically coupled between the first andthird IC chips; and a reference clock configured to generate and providea reference clock signal to each of the first, second, and third ICchips, wherein the first, second, and third SDMs are reset based on thereference clock signal.

Example 19 includes the subject matter of Example 18, and furtherincludes wherein the first, second, and third SDMs are reset based on asame particular cycle of the reference clock signal and when the first,second, and third PLLs are in a locked state.

Example 20 includes the subject matter of any of Examples 18-19, andfurther includes wherein the first, second, and third SDMs include asame sigma-delta sequence, and wherein resetting of the first, second,and third SDMs comprises aligning the sigma-delta sequence between thefirst, second, and third SDMs.

Example 21 includes the subject matter of any of Examples 18-20, andfurther includes wherein: the first IC chip is configured to receive atiming signal and the reference clock signal, the second IC chip isconfigured to receive the timing signal from the first IC chip and thereference clock signal, the third IC chip is configured to receive thetiming signal from the second IC chip and the reference clock signal,the first, second, and third IC chips are configured to generate first,second, and third reference time signals based on the timing signal andthe reference clock signal, and wherein resetting the first, second, andthird SDMs comprises resetting based on the respective first, second,and third reference time signals.

Example 22 includes the subject matter of any of Examples 18-21, andfurther includes wherein the first, second, and third reference timesignals are generated within a same particular cycle of the referenceclock signal.

Example 23 includes the subject matter of any of Examples 18-22, andfurther includes wherein the first IC chip is configured to generate afirst reference time signal based on a timing signal and the referenceclock signal, wherein the first IC chip includes a clock phase lock loop(PLL) configured to generate and provide a second reference clock signalat a higher frequency than the reference clock signal, wherein the firstIC chip is further configured to generate a second reference time signalbased on the first reference time signal and the second reference clocksignal, wherein the second reference time signal specifies a count of anumber of cycles of the second reference clock signal starting from aparticular cycle of the second reference clock signal, and wherein thefirst SDM is reset based on the second reference time signal.

Example 24 includes the subject matter of any of Examples 18-23, andfurther includes wherein the second reference time signal has a finercount resolution than the first reference time signal for a same timeperiod.

Example 25 includes the subject matter of any of Examples 18-24, andfurther includes wherein the reference clock signal comprises a firstreference clock signal, wherein an IC chip, comprising any of the first,second, or third IC chip, includes a first counter configured togenerate, based on a timing signal and the first reference clock signal,a first reference time signal indicative of a count of periods of thefirst reference clock signal, wherein the IC chip includes a secondreference clock configured to generate a second reference clock signalhaving a second frequency different from a first frequency associatedwith the first reference clock signal, wherein the IC chip includes aclock generator configured to generate, based on the first referenceclock signal, the second reference clock signal, and a phase selection,a third reference clock signal having a third frequency or phase shiftdifferent from the second reference clock signal, wherein the IC chipincludes a second counter configured to generate a third reference timesignal indicative of sub-periods of the third reference clock signal inaccordance with the phase selection, and wherein a SDM included in theIC chip is reset using the third reference time signal.

Example 26 includes the subject matter of any of Examples 18-25, andfurther includes wherein the second frequency is greater than the firstfrequency and the third frequency is less than the second frequency.

Example 27 includes the subject matter of any of Examples 18-26, andfurther includes wherein the third reference time signal indicates anumber of phase increments for each period of the third reference clocksignal that is 360 divided by a phase increment associated with thephase selection.

Example 28 is a radio frequency (RF) phase lock loop (PLL) including anoutput line; a phase detector electrically coupled to the output line; afrequency divider configured to form a feedback loop between the outputline and the phase detector, the feedback divider having a dividerratio; and a sigma delta modulator (SDM) electrically coupled to thefrequency divider, the SDM including a sigma-delta sequence configuredto define the divider ratio, wherein a particular cycle of a referenceclock signal resets the sigma-delta sequence to a particular sequencepoint.

Example 29 includes the subject matter of Example 28, and furtherincludes wherein the divider ratio comprises a fractional divider ratioor an integer divider ratio.

Example 30 includes the subject matter of any of Examples 28-29, andfurther includes wherein the RF PLL is included in a first integratedcircuit (IC) chip, further comprising a second RF PLL included in asecond IC chip, the second RF PLL including a second frequency dividerand a second SDM, the second frequency divider including a seconddivider ratio, the second SDM including a second sigma-delta sequenceconfigured to define the second divider ratio, and wherein thesigma-delta sequence and the second sigma-delta sequence aresynchronized to a same sequence point based on the particular cycle ofthe reference clock signal.

Example 31 includes the subject matter of any of Examples 28-30, andfurther includes wherein the particular cycle of the reference clocksignal is identified in accordance with a count of cycles of thereference clock signal, and wherein the count had a count resolutionthat is greater than a periodicity of the reference clock signal.

Although certain embodiments have been illustrated and described hereinfor purposes of description, a wide variety of alternate and/orequivalent embodiments or implementations calculated to achieve the samepurposes may be substituted for the embodiments shown and describedwithout departing from the scope of the present disclosure. Thisapplication is intended to cover any adaptations or variations of theembodiments discussed herein. Therefore, it is manifestly intended thatembodiments described herein be limited only by the claims.

What is claimed is:
 1. An apparatus comprising: a first integratedcircuit (IC) chip configured to receive a timing signal and a referenceclock signal; a second IC chip configured to receive the timing signalfrom the first IC chip and the reference clock signal; and a third ICchip configured to receive the timing signal from the second IC chip andthe reference clock signal, wherein the second IC chip is electricallycoupled between the first and third IC chips, wherein the first, second,and third IC chips are configured to generate respective first, second,and third reference time signals based on the timing signal and thereference clock signal, wherein the first, second, and third IC chipsinclude a respective first, second, and third phase lock loop (PLL), andwherein the first, second, and third PLLs are synchronized to each otherbased on the respective first, second, and third reference time signals.2. The apparatus of claim 1, wherein the first, second, and thirdreference time signals are generated within a same first particularcycle of the reference clock signal, wherein synchronization of thefirst, second, and third PLLs is initiated during a same secondparticular cycle of the reference clock signal, and wherein the firstparticular cycle of the reference clock signal is a different cycle thanthe second particular cycle of the reference clock signal.
 3. Theapparatus of claim 1, wherein the first, second, and third PLLs includerespective first, second, and third sigma delta modulators (SDMs), andwherein the first, second, and third SDMs include a same sigma-deltasequence.
 4. The apparatus of claim 1, wherein the first, second, andthird PLLs comprise radio frequency (RF) PLLs, and wherein the first,second, and third PLLs include respective first, second, and third sigmadelta modulators (SDMs).
 5. The apparatus of claim 1, wherein the first,second, and third PLLs include respective first, second, and third sigmadelta modulators (SDMs) and respective first, second, and third feedbackdividers, and wherein the first, second, and third SDMs control adivider ratio associated with the respective first, second, and thirdfeedback dividers.
 6. The apparatus of claim 1, wherein the first,second, and third PLLs include respective first, second, and third sigmadelta modulators (SDMs), and wherein synchronization of the first,second, and third PLLs comprises synchronizing the first, second, andthird SDMs to each other.
 7. The apparatus of claim 1, wherein thefirst, second, and third PLLs include respective first, second, andthird sigma delta modulators (SDMs), wherein the first, second, andthird SDMs include a same sigma-delta sequence, and whereinsynchronization of the first, second, and third PLLs comprisessynchronizing a starting point of the sigma-delta sequence in the first,second, and third SDMs to each other.
 8. The apparatus of claim 1,wherein the first IC chip is configured to generate a synchronizationsignal to trigger phase synchronization of the first PLL to the secondand third PLLs if the first reference time signal equals a pre-setreference time signal count value and the first PLL is in a lockedstate.
 9. The apparatus of claim 8, wherein the synchronization signalcomprises a first synchronization signal, and wherein the second IC chipis configured to generate a second synchronization signal to triggerphase synchronization of the second PLL to the first and third PLLs ifthe second reference time signal equals the pre-set reference timesignal count value and the second PLL is in a locked state.
 10. Theapparatus of claim 1, wherein the first PLL includes a feedback dividerelectrically coupled to a sigma delta modulator (SDM), and wherein theSDM is configured to define a divider ratio sequence of the feedbackdivider.
 11. The apparatus of claim 10, wherein the SDM includes asigma-delta sequence, and wherein the divider ratio sequence is afunction of the sigma-delta sequence.
 12. The apparatus of claim 10,wherein the feedback divider comprises a plurality of selective dividermodulators, and wherein a first selective divider modulator of theplurality of selective divider modulators is different from a secondselective divider modulator of the plurality of selective dividermodulators.
 13. The apparatus of claim 1, wherein each of the first,second, and third PLLs comprises one or both of an integer mode PLL or afractional mode PLL.
 14. The apparatus of claim 1, wherein at least twoof the first, second, or third IC chips are identical to each other. 15.The apparatus of claim 1, wherein at least two of the first, second, orthird IC chip are different from each other.
 16. The apparatus of claim1, wherein the first IC chip includes a clock phase lock loop (PLL)configured to generate and provide a second reference clock signal at ahigher frequency than the reference clock signal, wherein the first ICchip is further configured to generate a fourth reference time signalbased on the first reference time signal and the second reference clocksignal, wherein the fourth reference time signal specifies a count of anumber of cycles of the second reference clock signal starting from aparticular cycle of the second reference clock signal, and wherein thefirst PLL is synchronized based on the fourth reference time signal. 17.The apparatus of claim 16, wherein the fourth reference time signal hasa finer count resolution than the first reference time signal within asame time period.
 18. An apparatus comprising: a first integratedcircuit (IC) chip including a first phase lock loop (PLL), wherein thefirst PLL includes a first sigma delta modulator (SDM); a second IC chipincluding a second PLL, wherein the second PLL includes a second SDM; athird IC chip including a third PLL, wherein the third PLL includes athird SDM and the second IC chip is electrically coupled between thefirst and third IC chips; and a reference clock configured to generateand provide a reference clock signal to each of the first, second, andthird IC chips, wherein the first, second, and third SDMs are resetbased on the reference clock signal.
 19. The apparatus of claim 18,wherein the first, second, and third SDMs are reset based on a sameparticular cycle of the reference clock signal and when the first,second, and third PLLs are in a locked state.
 20. The apparatus of claim18, wherein the first, second, and third SDMs include a same sigma-deltasequence, and wherein resetting of the first, second, and third SDMscomprises aligning the sigma-delta sequence between the first, second,and third SDMs.
 21. The apparatus of claim 20, wherein: the first ICchip is configured to receive a timing signal and the reference clocksignal, the second IC chip is configured to receive the timing signalfrom the first IC chip and the reference clock signal, the third IC chipis configured to receive the timing signal from the second IC chip andthe reference clock signal, the first, second, and third IC chips areconfigured to generate first, second, and third reference time signalsbased on the timing signal and the reference clock signal, and whereinresetting the first, second, and third SDMs comprises resetting based onthe respective first, second, and third reference time signals.
 22. Theapparatus of claim 21, wherein the first, second, and third referencetime signals are generated within a same particular cycle of thereference clock signal.
 23. The apparatus of claim 18, wherein the firstIC chip is configured to generate a first reference time signal based ona timing signal and the reference clock signal, wherein the first ICchip includes a clock phase lock loop (PLL) configured to generate andprovide a second reference clock signal at a higher frequency than thereference clock signal, wherein the first IC chip is further configuredto generate a second reference time signal based on the first referencetime signal and the second reference clock signal, wherein the secondreference time signal specifies a count of a number of cycles of thesecond reference clock signal starting from a particular cycle of thesecond reference clock signal, and wherein the first SDM is reset basedon the second reference time signal.
 24. The apparatus of claim 23,wherein the second reference time signal has a finer count resolutionthan the first reference time signal for a same time period.
 25. Theapparatus of claim 18, wherein the reference clock signal comprises afirst reference clock signal, wherein an IC chip, comprising any of thefirst, second, or third IC chip, includes a first counter configured togenerate, based on a timing signal and the first reference clock signal,a first reference time signal indicative of a count of periods of thefirst reference clock signal, wherein the IC chip includes a secondreference clock configured to generate a second reference clock signalhaving a second frequency different from a first frequency associatedwith the first reference clock signal, wherein the IC chip includes aclock generator configured to generate, based on the first referenceclock signal, the second reference clock signal, and a phase selection,a third reference clock signal having a third frequency or phase shiftdifferent from the second reference clock signal, wherein the IC chipincludes a second counter configured to generate a third reference timesignal indicative of sub-periods of the third reference clock signal inaccordance with the phase selection, and wherein a SDM included in theIC chip is reset using the third reference time signal.
 26. Theapparatus of claim 25, wherein the second frequency is greater than thefirst frequency and the third frequency is less than the secondfrequency.
 27. The apparatus of claim 25, wherein the third referencetime signal indicates a number of phase increments for each period ofthe third reference clock signal that is 360 divided by a phaseincrement associated with the phase selection.